Patch "mISDN: hfcsusb: don't call dev_kfree_skb/kfree_skb() under spin_lock_irqsave()" has been added to the 4.19-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    mISDN: hfcsusb: don't call dev_kfree_skb/kfree_skb() under spin_lock_irqsave()

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     misdn-hfcsusb-don-t-call-dev_kfree_skb-kfree_skb-und.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 4d287bac29c22d9caf16a5697f4771310cf2f46b
Author: Yang Yingliang <yangyingliang@xxxxxxxxxx>
Date:   Mon Dec 12 16:41:37 2022 +0800

    mISDN: hfcsusb: don't call dev_kfree_skb/kfree_skb() under spin_lock_irqsave()
    
    [ Upstream commit ddc9648db162eee556edd5222d2808fe33730203 ]
    
    It is not allowed to call kfree_skb() or consume_skb() from hardware
    interrupt context or with hardware interrupts being disabled.
    
    It should use dev_kfree_skb_irq() or dev_consume_skb_irq() instead.
    The difference between them is free reason, dev_kfree_skb_irq() means
    the SKB is dropped in error and dev_consume_skb_irq() means the SKB
    is consumed in normal.
    
    skb_queue_purge() is called under spin_lock_irqsave() in hfcusb_l2l1D(),
    kfree_skb() is called in it, to fix this, use skb_queue_splice_init()
    to move the dch->squeue to a free queue, also enqueue the tx_skb and
    rx_skb, at last calling __skb_queue_purge() to free the SKBs afer unlock.
    
    In tx_iso_complete(), dev_kfree_skb() is called to consume the transmitted
    SKB, so replace it with dev_consume_skb_irq().
    
    Fixes: 69f52adb2d53 ("mISDN: Add HFC USB driver")
    Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
    Reviewed-by: Alexander Duyck <alexanderduyck@xxxxxx>
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/isdn/hardware/mISDN/hfcsusb.c b/drivers/isdn/hardware/mISDN/hfcsusb.c
index c952002c6301..c49081ed5734 100644
--- a/drivers/isdn/hardware/mISDN/hfcsusb.c
+++ b/drivers/isdn/hardware/mISDN/hfcsusb.c
@@ -337,20 +337,24 @@ hfcusb_l2l1D(struct mISDNchannel *ch, struct sk_buff *skb)
 		test_and_clear_bit(FLG_L2_ACTIVATED, &dch->Flags);
 
 		if (hw->protocol == ISDN_P_NT_S0) {
+			struct sk_buff_head free_queue;
+
+			__skb_queue_head_init(&free_queue);
 			hfcsusb_ph_command(hw, HFC_L1_DEACTIVATE_NT);
 			spin_lock_irqsave(&hw->lock, flags);
-			skb_queue_purge(&dch->squeue);
+			skb_queue_splice_init(&dch->squeue, &free_queue);
 			if (dch->tx_skb) {
-				dev_kfree_skb(dch->tx_skb);
+				__skb_queue_tail(&free_queue, dch->tx_skb);
 				dch->tx_skb = NULL;
 			}
 			dch->tx_idx = 0;
 			if (dch->rx_skb) {
-				dev_kfree_skb(dch->rx_skb);
+				__skb_queue_tail(&free_queue, dch->rx_skb);
 				dch->rx_skb = NULL;
 			}
 			test_and_clear_bit(FLG_TX_BUSY, &dch->Flags);
 			spin_unlock_irqrestore(&hw->lock, flags);
+			__skb_queue_purge(&free_queue);
 #ifdef FIXME
 			if (test_and_clear_bit(FLG_L1_BUSY, &dch->Flags))
 				dchannel_sched_event(&hc->dch, D_CLEARBUSY);
@@ -1344,7 +1348,7 @@ tx_iso_complete(struct urb *urb)
 					printk("\n");
 				}
 
-				dev_kfree_skb(tx_skb);
+				dev_consume_skb_irq(tx_skb);
 				tx_skb = NULL;
 				if (fifo->dch && get_next_dframe(fifo->dch))
 					tx_skb = fifo->dch->tx_skb;